This invention relates to medical devices. More specifically, the invention relates to a removable vena cava clot filter that can be employed to capture and treat blood clots in the vena cava of a patient.
Filtering devices that are percutaneously placed in the vena cava have been available for a number of years. A need for such filtering devices arises in trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. Patients having such medical conditions face an increased risk of thrombosis in the peripheral vasculature, wherein thrombi break away from the vessel wall, risking downstream embolism or embolization. For example, depending on the size, such thrombi pose a serious risk of pulmonary embolism wherein blood clots migrate from the peripheral vasculature through the heart and into the lungs.
Although the benefits of vena cava filters have been well established, improvements may be made. For example, conventional vena cava filters commonly become off-centered or tilted with respect to the longitudinal axis of the vena cava. When such filters are tilted, their struts engage the vessel walls along their lengths. This engagement increases the likelihood that the struts of these filters will become endothelialized in the vessel walls along a substantial portion of their lengths. When the filters become endothelialized, they often cannot be removed from the vasculature of the patient, even after the condition or medical problem that required the use of the filter has passed. The vena cava filters described in U.S. Pat. No. 7,625,390, the entire contents of which are incorporated herein by reference, overcome this disadvantage of conventional vena cava filters by including a plurality of secondary struts. The secondary struts are configured to centralize the filters in the blood vessel.
Despite the advantages of the improved vena cava filter described above, further improvements to vena cava filters are still possible. For example, existing vena cava filters do not provide a means of treating captured blood clots. Therefore, the capture of especially large or numerous blood clots by existing filters may cause such filters to become clogged. Moreover, the blood clots captured by such filters may become dislodged during filter retrieval.
While it is possible to address the aforementioned risks by administering a systemic anti-coagulant, this approach also poses certain risks. For example, systemic anti-coagulant administration may be associated with an increased risk of intracranial hemorrhage. Moreover, since the effects of systemic anti-coagulant administration vary significantly from patient to patient, systemic administration requires significant and careful monitoring of the patient.